Luminescence decay kinetics of Ge related center in silica

Detailed measurements of luminescence decay kinetics in Ge doped silica fiber have been carried out for different excitation energies from 3 to 7.7 eV and luminescence detection energy from 2 to 4 eV. The decay kinetics of luminescence is rather well approximated by an exponent. A distribution of time constants over the range 90-130 μs in decay exponential approximation is pointed out. This distribution is due to structural non-equivalency of Ge centers in the disordered glass structure. At 10 K the life time increases up to 150-450 μs, and it is explained as influence of zero-field splitting of the triplet state. The spectra of luminescence and its excitation also are affected by inhomogeneous broadening. The excitation with photons above 6.4 eV causes appearance of thermally stimulated luminescence also.